1. Field of the Invention
The present invention relates to an engine controller capable of switching combustion modes between compressed self-ignition type combustion and spark ignition type combustion.
2. Description of Related Art
In internal combustion engines (hereinafter, engines) used for automobiles and the like, a compressed self-ignition type gasoline engine (hereinafter, a compressed self-ignition engine) which compresses an air-fuel mixture to cause self-ignition combustion (hereinafter, compressed self-ignition type combustion) attracts attention as the one which provides improvements in fuel efficiency and exhaust performance at the same time. As compared with spark ignition type combustion in which an air-fuel mixture is ignited by spark of an ignition plug and combusted, the compressed self-ignition engine can reduce a fuel consumption rate by increase in efficiency due to high compression, reduction of pump loss due to lean-burn, and improvement in degree of constant volume due to rapid combustion, and can reduce an NOx concentration in exhaust gas due to a low combustion temperature. Therefore, the compressed self-ignition engine can realize both fuel efficiency and exhaust performance at the same time.
When the compressed self-ignition engine is applied to an automobile, it is proposed to carry out both of spark ignition type combustion and compressed self-ignition type combustion by switching them to realize engine torque required by a driver.
As a document which discloses the art relating to switching of the combustion mode from the compressed self-ignition type combustion to the spark-ignition type combustion, JP-A-2006-274951 and JP-A-2004-36575 are cited.
JP-A-2006-274951 discloses the art which improves response delay of an intake amount by controlling the timing of an intake valve (intake valve closing time) in accordance with intake pipe pressure during a response delay period of the intake amount in throttle control when switching the combustion mode from the compressed self-ignition type combustion to the spark ignition type combustion, so that the combustion switching is realized without torque variation and exhaust deterioration.
JP-A-2004-36575 discloses the art which controls a fuel injection amount and ignition time in accordance with the intake pipe pressure during a response delay period of the intake amount in throttle control when switching the combustion mode from the compressed self-ignition type combustion to the spark ignition type combustion, so that the combustion switching is realized without torque variation.